Some lighting devices are generally capable of emitting light within virtually any color range. This diversity of color emitted may be accomplished via a combination of various colored primary light sources emitting light at varying luminosities. Commonly, in devices that combine light to create various colors, the primary light sources include red, blue, and green colored light.
Red, green, and blue are traditionally known as primary additive colors, or primaries. Additional colors may be created though the combination of the primaries. By combining two additive colors in substantially equal quantities, the secondary colors of cyan, magenta, and yellow may be created. Combing all three primary colors may produce white. By varying the luminosity of each color emitted, approximately the full color gamut may be produced.
In systems using three primary colors to control the luminosity of the emitted light, the brightness of the emitted colored light may be controlled by altering the brightness of the primaries corresponding to the output color desired. If a white output color is desired, all primaries would be required to emit light at full luminosity. In a lighting system that utilizes LEDs to emit light, operating every LED at full luminosity may require using an undesirably large amount of energy and may produce and excessive amount of heat. Therefore, there exists a need for an efficient system to emit light of virtually any color included within the full color gamut without the inefficient operation characteristics of the prior art.
In attempts to satisfy this need for the efficient emission of colored light, inventions in the prior art have disclosed adding a white light source to supplement the primary color light sources. By including an additional white light source, the white light may provide additional brightness without requiring the primary light sources to operate at full luminosity. However, most lighting source signals do not contemplate the inclusion of a white light source, resulting in signals that cannot drive the white light source of the modified lighting device.
Previous disclosures have described methods of estimating a white input signal from an RGB (red-green-blue) input signal by using various methods. U.S. Patent Application Publication 2007/0157492 to Lo et al. discloses approximating a white value by comparing grayscale values of the primaries. However, the approximation disclosed in the Lo et al. '492 publication requires discarding luminosity values, resulting in potentially inaccurate results.
U.S. Pat. No. 7,728,846 to Higgins et al. discloses converting an RGB signal to an RGBW (red-green-blue-white) through complex matrices and algorithms. However, the Higgins et al. '846 patent outputs a signal that drives a white light source in addition to the primaries, requiring the operation of a large number of power consuming elements than before conversion of the signal may occur.
The proposed solutions included in the prior art that create a signal to drive a white light source commonly drive the white light source in addition to the preexisting primaries. By adding a new lighting source, the proposed solutions of the prior art may not operate with optimal efficiency characteristics. Additionally, the solutions proposed in the prior art contemplate converting an RGB into an RGBW signal. As a result, any additional input signal formats, such as the commonly used xyY color space, must first undergo conversion operations which may be computationally intensive and wasteful of energy. Furthermore, the disclosures in the prior art require the use of light sources defined within the full color gamut to reproduce light in various colors, contributing to inefficient operation of the devices included in the prior art.
There exists a need for a lighting signal converter that may accept a source signal capable of defining a colored light in a two spatial plus luminance dimensional color space that includes the full color gamut, such as the xyY color space, and produce an output signal that is defined in a three dimensional color space defined by a subset gamut of the full color gamut. There further exists a need for a lighting signal converter that outputs a signal to efficiently drive a minimal number of primary light sources along with a high efficacy light source.